Second-hand Smoke Linked to Increased Risk of Miscarriage, Stillbirth

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Women exposed to tobacco smoke for a long time may have an
increased risk for miscarriage, experiencing stillbirth or a
pregnancy outside the uterus, according to a new study.

The researchers looked at the medical information of about 80,000
post-menopausal women to examine how their levels of
exposure to tobacco smoke may have affected their
pregnancies in the past.

About 41,000 of the women in the study had never smoked. However,
those within this group who were exposed to second-hand smoke for
more than 10 years during childhood, or as an adult at home or at
work, were 17 percent more likely to miscarry, 55 percent more
likely to give birth to a
stillborn child, and 61 percent more likely to have ectopic
pregnancies, in which the embryo is implanted outside the uterus
and cannot survive, compared with women who were never exposed to
second-hand smoke.

The findings "suggest that lifetime second-hand smoke exposure
contributes to a great number of adverse pregnancy outcomes each
year," the researchers wrote in their study published today (Feb.
26) in the journal Tobacco Control. [ Never Too
Late: 5 Habits You Should Still Quit ]

The effects of cigarette smoking by pregnant women has been
studied extensively in the past several decades, and is known to
be associated with increased risk of infertility, preterm birth,
miscarriage and stillbirth and other pregnancy complications, the
researchers said.

In line with earlier findings, the participants in the new study
who were smokers during their reproductive years had 16 percent
higher risk of miscarriage, and 44 percent higher risk of
stillbirths and
ectopic pregnancies, compared to women who weren't smokers.

Unlike active smoking, the effect of exposure to second-hang
smoke on reproductive health is less clear, the researchers said.

Cigarette smoke contains more than 4,000 chemicals including
carcinogens and toxic heavy metals. It is not fully known how
these chemicals may affect pregnant women or their fetuses, but
one possibility is that the
hormone-disrupting properties of some of these
substances can interfere with the development of the fetus,
studies have suggested.

In the study, about 5,000 of the women (6.3 percent) were current
smokers, about 35,000 (43 percent) were smokers in the past, and
about 41,000 (50.6 percent) were non-smokers.

One-third of the women reported they had miscarried at least
once. About 4 percent had experienced a stillbirth, and 2.5
percent had had an ectopic pregnancy.

Several studies have suggested that the health of pregnant women
and babies improved after smoking bans in public places were
enacted and women's exposure to second-hand smoke was reduced.
Last year, a study from Scotland found that
rates of preterm deliveries dropped following a smoking
ban.

In the United States, national studies show that there was a 75
percent decline in second-hand smoke exposure between 1988 and
2002, the researchers said, and this trend seems to be in line
with 4 percent decline in reported miscarriages and 11 percent
decline in stillbirths during that period, the researchers said.
However, other factors such as improved health care and increased
public awareness have also likely played a role in these
declines, the researchers noted.